Field
Embodiments disclosed relate to a light guide plate and a planar light source device.
Description of the Related Art
A representative example of light-emitting elements is Light-Emitting Diodes (LEDs), which convert electrical signals into infrared light, visible light, and the like using the characteristics of compound semiconductors. LEDs are used in, for example, home appliances, remote controllers, electronic display boards, display devices, and various automation devices. The fields in which LEDs are used are gradually becoming more numerous.
A planar light source device equipped with LEDs is a device that converts light, which is emitted in a point light source form from LEDs, into a planar light form. The planar light source device may be used in a display apparatus such as a liquid crystal display apparatus, and may be used in a variety of lighting apparatuses.
In a conventional light guide structure, light is introduced from a light source, located at one side when viewing a cross-section of a light guide unit, into the light guide unit so as to be guided to a light emission surface or a surface opposite to the light source. A light guiding means is a total reflection or light emission means based on the difference in the index of refraction, and this means uses a pattern or shape to cause light to be emitted from the light emission surface.
Referring to FIG. 16, there are arranged a light guide plate 300, which has a light introduction surface 310 located at one side surface, and a light source module 200 adjacent to the light introduction surface 310 of the light guide plate 300.
Here, light, provided from the light source module 200, is introduced into the light introduction surface 310 to thereby undergo total reflection and diffusion inside the light guide plate 300.
At this time, the light guide plate 300 is generally formed of a transparent material which has a higher index of refraction than air. However, the transparent light guide plate 300 absorbs some of the light, having a given wavelength, from the light source module 200. Thus, the light emitted from the light source module 200 is changed in color by passing through the light guide plate 300. In particular, the light emitted from the light guide plate 300 is gradually changed in color with increasing distance from the light source module 200.
In recent years, a glass material having good transparency and rigidity is used as the material for the light guide plate 300. When white light from the light source module 200 is introduced into the glass material, the glass material absorbs bluish light (in a wavelength band from 400 nm to 440 nm). Thus, the light guide plate 300, which is distant from the light source module 200, may problematically emit light in which a yellow color is intensified.
In the case where a planar light source device emits other colors of light, rather than emitting white light, the liquid crystal display apparatus employing the planar light source device suffers from the problem of color deviation.